1. Field of the Invention
This invention relates to an image forming apparatus which can reduce the size of an input image, and more particularly, to an image forming apparatus suitable for image communication, such as a facsimile apparatus or the like.
2. Description of the Related Art
In conventional image communication apparatus, such as facsimile apparatus or the like, a received image becomes in some cases an image that is longer than a standard format because a header or the like is added, and therefore cannot be recorded on standard format recording paper. In order to overcome such a problem, a received image is recorded by reducing received data in the sub-scanning direction. In this case, a method of reducing the size of an image by skipping received image data for one line at a constant interval (i.e., skipping the data of every nth line for some natural number n) has been widely adopted.
In current image communication apparatuses, the transmission side selects one line density from among a plurality of line densities in the sub-scanning direction, reads an image with the selected line density, and transmits the read data. The reception side performs image formation based on received data using recording means, such as a thermal print head or the like.
Standard (3.85 lines/mm), fine (7.7 lines/mm) and superfine (15.4 lines/mm) line densities in the sub-scanning direction are provided. Recording means at the reception side can record with the superfine (15.4 lines/mm) line density in the sub-scanning direction. When received data have the standard (3.85 lines/mm) line density, an apparatus at the reception side moves recording paper with a pitch of 1/15.4 mm and records received data for one line repeatedly four times at every movement. When received data have the fine (7.7 lines/mm) line density, the apparatus moves recording paper with a pitch of 1/15.4 mm and records received data for one line repeatedly twice at every movement.
As described above, when reducing the size of a received image in the sub-scanning direction, received data for one line are skipped at a constant interval (for example, in the case of size reduction to 90%, received data for one line are skipped for every 10 lines). Hence, data of intervals of 1/3 mm and 1/7.7 mm are lost when received data have the standard line density and the fine line density, respectively, causing deterioration in the recorded image.
A method of smoothly realizing a step in an image by smoothing processing for received image data has been known. In this method, smoothing correction is performed after skipping received original lines when reducing the size of a received image. As a result, information on skipped lines cannot be utilized in smoothing correction processing, causing deterioration in image quality.